![]() Hydrothermal vents, geysers that produce super-hot, mineral-rich water, help support a diverse community of organisms found along the ocean floor.Ĭhemoautotrophs, bacteria that can synthesize organic compounds without natural light, thrive near these vents because of the warmth and the large amounts of hydrogen sulfide and other minerals they can use as nutrients. Although the water in this region is very cold-around 3° Celsius, the abyssal zone supports many species of invertebrates and fishes. The very deepest parts of the oceans form the abyssal zone. Animals and plants found in the benthic zone include seaweed, bacteria, fungi, sponges, sea anemones, worms, sea stars, and fishes. It consists of sand, silt, and decaying organisms. If the water is clear, photosynthesis can occur at depths of up to 500 feet, although 100 to 300 feet is more usual. The topmost layer of the ocean is affected by the sun’s light, and this area is home to plankton and a variety of fish species. The pelagic zone is made up of the world’s open oceans. They are composed of relatives of hydras called cnidarians, and the living polyps are covered by a hard shell of calcium carbonate.Ĭnidarians are associated with photosynthetic algae, which provide the cnidarians with nutrients.Ĭoral reefs are home to a wide variety of invertebrates, fishes, sea urchins, and other organisms. Organisms that live in the intertidal zone, the seashore region between high tides and low tides, have to respond to the mechanical action of waves, as well as a daily cycle of drying out and flooding.Ĭoral reefs are widely distributed in warm shallow waters. Seaweeds, marsh grasses, and, in the tropics, mangrove trees are typical estuarine plants. Estuarine animals and plants are adapted to respond to changes in salinity that occur along with the rise and fall of the tides. Today, just over 100 million acres remain.Įstuaries and their associated wetlands, called mudflats and saltmarshes, are areas in which salt water meets freshwater, usually at the mouth of a river. ![]() In the United States, before white settlers arrived there were almost 400 million acres of wetlands. Over the past few hundred years, humans have destroyed wetlands to clear land for cities. Some wetlands are only periodically flooded, while others are wet throughout the year. Bogs, marshes, and swamps are all wetlands. Wetlands are areas saturated with moisture. Near the wider mouth of a river, the bottom is usually composed of silt from the deposition of sediment over long periods of time. Rivers generally carry more nutrients and more sediment from soil erosion than streams do. Rivers and streams are bodies of fresh water that continually flow in one direction. Shallow lakes have higher nutrient levels, usually because they are warmer, and sunlight allows more phytoplankton to flourish. Large bodies of fresh water are called lakes. The abyssal zone actually consists of the very deepest benthic zones. These are the intertidal zone between the low and high tide marks coral reefs the open ocean, or pelagic zone the ocean bottom, or benthic zone and the deepwater trenches of the abyssal zone. Marine biomes are often grouped together as the oceanic biome, which is subdivided into a number of zones. Freshwater biomes include lakes, rivers, wetlands, and estuaries. Aquatic biomes are categorized as freshwater and marine biomes.
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